You can't turn the Steelers logo into a bunch of marijuana leaves ... or else you'll face the wrath of the NFL ... so says a pot group in Pittsburgh that just got lit up with a nasty legal threat.
The bud beef is all over the logo for the Pittsburgh chapter of NORML -- a massive nonprofit group dedicated to legalizing weed.
They've been using a logo similar to the famous Steelers design for years -- with the asteroids swapped out with red, yellow and blue ganja leaves.
Problem is ... some square at the NFL caught wind of the logo and fired off a cease and desist -- warning the group to 86 the design .. or else! (Guess that paranoia was justified this time).
Turns out ... the people at NORML are more smokers than fighters and told us they're backing down and plan to change the logo ASAP because they don't want a war with the NFL.
Two NORML honchos, Patrick Nightingale and Jason Cole, tell TMZ Sports they're already coming up with a Pittsburgh-themed replacement logo -- "Maybe Andrew Carnegie holding some weed."